In the manufacture of integrated electronic components manufacturing tolerances are set that require trimming of the components after they have been produced by mass production operations. On the basis of the necessary external connections of the integrated circuit components it is known to produce hybrid components in which an integrated circuit in the form of a semi-conductor chip is combined with discrete components. If the so constituted hybrid component is made in such a way that the circuit elements necessary for adjusting the operation of the components are provided as discrete circuit elements, it is possible by modifying these discrete circuit elements to trim the electrical properties of the component. Thus it is possible, for example, to provide a resistance that determines the operating behavior of the component by the use of thin film technology and to produce the trimming of the entire component by affecting this resistance.
German published Patent Application (OS) 1 640 518 discloses a method and apparatus for trimming active electrical circuit elements in which the adjustment of the circuit element is carried out by removing material from a resistor or from another circuit element that is variable in its electrical characteristics by removal of material. The apparatus for performing this method includes a sand blasting device for removal of material by which a resistance provided as a layer on a substrate can be progressively reduced in extent until the electrical circuit element has the desired characteristics. With the apparatus shown in that published patent application it is also possible to control the process of removal of material with reference to the desired dc characteristics of the circuit element.
It is further known to change, by removal of a material by means of a laser, circuit elements of an integrated circuit provided in the form of layers on a substrate.
A disadvantage of the known methods is that in making use of a laser or a sandblasting device and, it is necessary to score the substrate at least lightly. The risk here arises that the region of the substrate at which material must be removed may be the starting point for undesired microcracks. A further disadvantage of the known process is that the electrical properties of the layer material are changed along the incision resulting from the removal of material. Furthermore, the known process can lead to distorting the paths of conductors and resistances and thereby causing the critical current density to be exceeded in these paths.
A method was disclosed in the publication "Thin Solid Films" vol. 12 (1972) pages 335-339, in which by oxidation of a tantalum layer provided on a substrate the electrical properties of the tantalum layer can be modified. The tantalum layer serving as a circuit element of an integrated circuit is in this case covered with an electrolyte in to which an electrode dips. If now a negative voltage is applied to the electrode and a positive voltage is applied to a conducting layer making contact with a boundary of the tantalum layer, a flow of current is provided from the voltage source over the electrode, through the electrolyte, the tantalum layer and the conducting layer back to the voltage source. By selection of a suitable electrolyte a portion of the metallic tantalum layer can be changed into a non-conducting compound. If the electrolyte, for example, contains OH.sup.- ions, the tantalum at the boundary surface between electrolyte and tantalum layer is converted into tantalum oxide according to the equation: EQU 2 T.sub.a.sup.5+ + 10 OH.sup.- .fwdarw. Ta.sub.2 O.sub.5 + 5H.sub.2 O
in this manner it is possible by a chemical reaction in a thin film path to carry out a trimming of an electrical component.
A disadvantage of the process just described is that with such an anodizing current the thin film path carries a current, so that the trimming of the component as a whole during typical operation cannot in every case be performed, because the anodizing current necessary for the electrolytic conversion process can impair the operating characteristics of the component to such an extent that a continuous adjuestment is no longer possible. If it is desired to measure the operating characteristics of the component during the trimming operation, the trimming operation must be performed iteratively, i.e. the trimming can be performed only in small steps and after each step the characteristic values of the component must be measured anew. That, however, is very expensive and time consuming and therefore not practically usuable in large scale manufacture of integrated circuit elements.